Signaling system



Patented May I, 1%329.

1 UNITED STA'IES".

PATENT .OFFICE.

mnonn 11:. rnun-nn, on WYOMING, NEW JERSEY, essrenon TO BELL mnnrnonnLABORATQRIES, mconromrrnn, on vnnw YORK,'1T. Y., A conrona'rron on NEWYORK.

SIGNALING SYSTEM.

Application filed January '29, 1927. Serial No.- 164,414.

This invention relates to signalingsystems and particularly to telephonesystems wherein call signaling is accomplished by current within thevoice frequency range. The pri- 'mary purpose of the invention is toelimion signaling;

nate or-reduce the chance of false ringing 'It has been structionandarrangement of the present day long distance and toll telephonellnes,

signaling current is most' eifectively em-. ployed when it is within thevoice frequency range. Usually there is provided a relay which, whilewithin the voice frequency range, is-near the boundary thereof so thatfore, transmits a false signal. The presentthe ordinary.andmost-frequently used tones do not affect such relay. There are t mes,however, when particular frequencies are set up by the'voice to whichsuch relay will respond and the response of such relay, thereinventionobviatesthis difiiculty by employ ing another relay to render thesignallng relay inelfective Such other relay will not not responddirectly to the current designed to operate the first relay, but willreadily respond to other voice currents or current.

The invention has its preferred embodiment, specifically stated, in arelay for relaying calling signals which is made responsive only to'current of a particular'frequency within but near the boundary of thevoice frequency range, in combination with another relay upon which theincoming currents are simultaneously impressed, for renderingkthe firstrelay ineffective, the second relay ing made responsive to the most.fre-

quently occurring frequencies in the voice range; The first relay issharply. tuned, whereas the'second is broadly tuned so that it willrespond to currents over a wide range of frequencies; The second relay,moreover, is somewhat slow in action and will, therefore, maintain .itsarmature operated if the voice currents include for an instant, the.current ofthe frequency to which the signaling relay responds. The voicecurrents are generally made up of a pluralityof different frequenciesand when a frequency to which the signaling relay will respond istransmitted, it is generally accompanied by some 'of the more ordinarilyoccurring voice frequencies so that the second or controlling foundthat, due to the .con-' relay will be maintained operated. Preferablythe controlling relay controls a circuit 'in which there is no currentflow under normal condltlons so that its contacts, due to 'almo'stcontinuous operation, will not be unduly worn or corroded by sparking.

invention and consists, of. a diagrammatic re resentationof a signalreceiving circuit. 1g. 2 shows an alternatlve form of the A morecomplete description of the inveninvention and consists of adiagrammatic representation of a signal receiving circuit;

Fig.' 3 is a curve showing the relation between speech amplitude andfrequency.

In Fig. 1 the conductors 1 and 2 may be connected to a telephone line.These conductors extend to the primary windings of a repeating coil3,the sec'ondary winding of which is included in the grid circuit of avacuum tube amplifier, the grid being desi nated by the numeral 4.- Thefilament 5 1s energized by the .grounded battery 7. The plate 6 extendsinto thesignal receiving .circu t. Relay 8 responds to signaling currentand relay 9. respo nds't'ovoice current.

incoming signal-current will be trans-' formed by the repeating coil,-will-afiect the grid 4 and set up in the circuit including plate 6 acorresponding current. This current will travel from the plate 6 throughthe condenser 10, the winding of relay 8 to ground at battery 7 and willthereby-energize relay 8. LA parallel circuit extends from plate 6v trough the winding of relay 9, the plate battery 11 to ground',-butrelay'9 will not respon Condenser 12 connected between plate. 6 andground is employed in connection with condirectly to'msignaling'current.

denser 10 for sharply tuning the circuit of relay 8,condenser 10 alsoserving toprevent a drain on battery 11. Condenser 12 is also used .totune the circuit of relay 9.-

Upon the response of relay 8 a circuit is established from groundedbattery, resistance 13, winding of relay 14,- winding of relay 15 toground. Relay 14 becomes energized and short-circuits relay 15 throughthe back cont-act of relay 9. Relay 1.5 becomes deenergized whereupon acircuit for shunting relay 16 is established through the front .38 willrespond and byattracting its armasignal 47.

contact of relay 14 and the back contact of relay 16. and establishes anobvious circuit-for slgnal Relay '16 becomes deenergized Duringconversation on the telephoneylinc the voice currents are transformed bythe re peating coil 3, affect the grid 4, and produce in the circuitincluding plate 6 corresponding' currents. These currents do not affectrelay 8 but will affect relay 9.. Relay -9 attracts its armature andopens the previously described circuit for shunting relay '16 so .thatshould the current of the frequency to which relay 8 is tuned occur theconsequent operation of-relay 8 and relay 14' will be without effect. Itshould be noted that'relay 9 opens a circuit which under normalconditions is opened at two other points and that consequently relay 9which isoperated mostof the time does not break any current flow at itscontents.

Fig. 2 shows a somewhat similar arrangement except that here no vacuumtube amplifier is indicated although one may be used without theexercise-of invention. Conduc tors 31 and 32 may be connected. toa'telephone line. Relay 38 is tuned by me'ansof impedancecoil 33 andcondenser'34 toa definite signaling frequency whereas relay 39 isbroadly tuned to respond to voice currents.

When a signalingeurrent is received relay turc will open ashort-cireuitabout the wind- "ing of relay. 45. Relay now becomesoperated in the circuit including grounded-bab tery 35, resistance 36,the armature-and back contact of relay 39, the. winding .of'relay 45- toground. Relay .45 byatt'racting its armature shunts the winding of relay46 which,

establishes an' obvious energizing circuit for During conversation relay39 responds to voice currents and relay 38remains inert. Relay 39 inattracting its armature opens the energizing circuit for relay 45 sothat if a current of the proper frequency to operaterelay'38 occurs theremoval of the short-' effective.

circuit from: about the relay45 will be in- Fig. 3 represents therelationbetween-current strength and frequency for voice currents. Thecurve shows that the current strength increases with increase "inthe/frequency up to a certain. point'whereupon it turns and thereafterdecreases- The peak is at the most common voice frequency and the voicerelay is tuned torespond to currents in abroad zone including thispeak.The signaling relay is more sharply tuned at point high up in thefrequency values.

The voice relay may be. adjusted so that it is sufiiciently sensitive tooperate on ordinaryspeech, amplitudes" so that thellikelihood of asignaling frequency of sufficient amplitude tooperate the signalingrelay being present most common occurrence.

is very small. Any. increase, in speech strength making signalingoperation likely,

provides, therefore more positiveaction in I the voice relay.Infaccordance with this methndofadjustment the voice relay is held upcontinuously during talking and renders the signaling relay ineffective.

The voice relay may on'the other hand be so adjusted that it'does notrespond to ordinary speech amplitudes but will respond" to'gr'eateramplitudes. The ordinary speech amplitudes will not operate theslgnaling relaybut if they are increased to the point where, should theycontain a signaling frequency, the signaling relay would operate,

then the voice relayv would operate and render the signaling're'layineffective.- The curvein Fig. 3 shows that there will be moreoperatingenergyaround the frequencies of most common occurrence to whichthe voice relay is'tuned and at the same time less at the'highersignaling frequencies. This provides a natural increase-in sensitivityto the voice relay and decreases the likelihood of its failing tooperate in either case. In accordance then with this second method ofad-v jus'tment neither the 1 voice relay nor the signaling relay operatewith ordinary speech, but the'voice, relay is muchmore likelyto operateif the speech volume is increased. r i

What is claimed is:

1. Ina signaling system, arelay for relaying signals responsive tocurrents of a .narrow band of frequencies near'the boundary .of the bandof voice frequencies and another relay for rendering ineffective said.first relay-responslve to currents of a'wide band of voice frequency. Iv

2. In a signaling system, a relay for relaying signalsre'sponsivetoalternating current of a definitefrequency and another relay to renderineffectivesaid first relay responsivetocomposite currents of aplurality of frequencies and including said definite frequency.

3. In asignaling system, a relay for relaying the signals responsivetoalternating about a different definite frequency.

laying signals-responsive to a narrow band of voice frequency. currentsof infrequent occurrence and another relay for renderlng ineffectivesaid first relay responsive to a wide band of voice frequency'eurrentsof 5. In asignaling systein, a lay and a second relay, saidrelays beingselectively responsive to currents transmit-' ted theretoover said line, a signal circuit in cluding a normally open link, meansunder 7 control of said first relay for closing said link and meansunder control of said secon relay for opening said link.

6. In a signaling system, a sharply tuned relay for actuating a signalresponsive to alternating current of a definite frequency and a broadlytuned relay for renderingsaid' first relay ineffective, said broadlytuned relay being responsive to currents of 1 voice frequency currentsit Will remain actuated during the infrequent occurence of currents ofsaid definite frequency.

In Witness whereof, I hereunto subscribe my name this 27th dayofJanuary, A. D., l

1927. HAROLD M. PBUDEN.

